BP has frequently had a tense relationship with Russia over TNK-BP, which produces a third of the company's oil. Last week, the Russian ambassador to the UK stated Moscow would seek "guarantees that [the partnership] will continue to work", and President Dmitry Medvedev said that he fears the spill could "annihilate" BP.

In further developments:

• BP said the threat of a hurricane has delayed its efforts to increase the amount of oil being captured from the leak until next week.

• The company's shares closed up 1pc at 308.25p on news that the storm, called Alex, will probably pass by without worsening the slick.

• BP admitted that the cost of the clean-up has now soared to $100m (£66m) a day, taking the total to $2.65bn. The daily rate has risen from $3m at the beginning of the crisis.

Meanwhile, The Daily Telegraph has learnt that a group of oil majors, thought to include Chevron, ConocoPhillips, ExxonMobil and Royal Dutch Shell, is preparing to present the US government with proposed changes to deepwater safety rules. The move is understood to be an attempt to pre-empt any move by America to insist on relief wells for all drilling.

BP says the leak will be plugged with a relief well by August, but the method takes several months after a spill occurs. US politicians have been calling for all operators to drill relief wells in case of an accident. This could double the cost of deepwater drilling, according to Geoffrey Maitland, professor of energy engineering at Imperial College.